Much attention has been given to the toxicologic effects of plasticizers to which patients may be exposed via components of dialysis equipment, plastic tubing and plastic blood bags. Although numerous toxicologic studies have been able to demonstrate effects only after massive doses, concern persists that these compounds may be deleterious. Consequently, suggestions have been made to limit the plasticizer exposure of patients by removing it from contact with body or parenteral fluids wherever possible. To document the specific effect of the common plasticizer DEHP on red cells, this study was designed to investigate changes occurring in the red cell membrane in the presence and absence of DEHP in stored blood. Significance of these changes will be evaluated through 51chromium survival studies of autologous red cells stored in the presence or absence of DEHP. Results from the first phase of this project demonstrate that units stored with DEHP had better 24 hr red cell survivals than those stored without DEHP. Results of a paired study of 10 normal blood donors showed that red cells stored with DEHP have a mean 24 hour 51Cr red cell survival that is 24% higher than red cells stored without DEHP (p less than 0.001). These data suggest that DEHP has a beneficial effect on red cell membranes during storage. Removal of such plasticizer from blood storage systems may be detrimental.